Scored a case of this stuff made by Castrol at a garage sale. Supposedly heavy duty full synthetic ATF. Anybody use this in a built 727?

I do, no issues in 7 years.

What is your application, and why did you start using it?

Street/strip 500ci, 727rmvb, 4.56 gears. After assembling the the car I started using tranSynd from the start by a buddy who worked on/with Aliison.

Thanks for the vote of confidence!

Ive been told most performance clutch material was developed around gm products so the correct fluid to use in a built transmission is Dexron VI.

It will work but you wont notice much of a difference between it and anything else. I fooled with hydraulic fluid years ago and all it did was make my wallet lighter and my eyes hurt trying to read the dipstick because it was clear.

I just went through my glide that I have raced since oh, 1998 or so.....Has the red clutches in it and I reused them again, because, they still look like new.

Have always ran type F in it.